A conventional key structure of a portable electronic device substantially comprises a spring-type structure and a film-type structure. In the spring-type structure, a pin is disposed on one side of a key body with respect to an electrical switch of the portable electronic device, and a spring is disposed between the key body and the electrical switch. The film-type structure is made of rubber, and the film-type structure is disposed in a pre-designed key area of the electronic device. No matter the spring-type structure using the spring for elastic recovery or the film-type structure made of rubber, after being used for a long time, the elastic fatigue of the material occurs, thereby influencing the sensitivity of the key structure.